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noisy tach signal

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chris_hand(at)comcast.net
Guest

Posted: Wed Jun 03, 2009 11:00 pm Post subject: noisy tach signal

I'm having a lot of trouble getting a good tach reading on my IK-2000 engine 

monitor using a Hall effect sensor on a Slick mag and am looking for

suggestions on what to try next.  I've tried multiple different wiring 

routings and tried 0.1 uF capacitor between signal lead and ground as well

as between +5V power lead and ground, with no success (problem actually got 

worse when I added the caps so I took them back out).



History is that I initially had dual P-mag setup with tach sensor reading 

off right P-mag.  Tach worked fine in that configuration.  At about 26 hours

total time I replaced the left P-mag with an impulse coupled Slick mag, 

still taking tach signal off right side P-mag.  In that configuration I had

noise issues causing problems with the tach reading at power settings below 

about 1800 rpm (engine / prop combo is O-360, fixed pitch Sensenich).  The

issue only showed up on throttling back when in flight; didn't see it on the 

ground except after landing when I had the problem in flight.  Those tach 

problems were resolved by tying the Slick mag p-lead up a little further 

away from the tach sensor leads (although they were already seperated by at 

least 6 or 8 inches at closest approach).



This past weekend I changed out the right side P-mag for non-impulse coupled 

Slick mag and installed a Hall effect sensor in the mag vent hole for

feeding the IK-2000 tach sensor lines.  This was the sensor suggested by 

IK-Technologies.   Ground testing shows good tach readings only at rpms

above about 1000-1200 rpm but after 10 or 15 minutes of flight time it 

starts reading low and erratic at power settings below about 2000 rpm,

becoming completely unusable at approach and idle power settings.  If I 

secure the right mag at any time (ground or in-flight testing), the tach

reading is steady and appears accurate.  So the noise is being introduced by 

the right mag when it is operating, but with the mag not firing, the sensor

installed on that mag works great.



I am using the factory supplied sensor wiring harness, which uses twisted 

pair wiring with none of the leads being shielded.  I had extra lengths in

this harness when I installed it so have the extra length coiled up under 

the forward top skin.  For lack of any other ideas, I'm thinking about

removing the factory harness and building a new one using 3-wire shielded 

cable for the tach sensor lines.



Has anybody else on the list run into tach signal noise issues when using 

standard mags with Hall effect sensor?  Any suggestions on what else I can

do to fix this?  (aside from going to a different sensor type or stand-alone 

tachometer)



Thanks in advance for any suggestions!



Chris

RV-6A, N731CK, 55 hrs

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chris_hand(at)comcast.net
Guest

Posted: Tue Jun 16, 2009 10:44 pm Post subject: noisy tach signal

I have been unable to solve this problem so far and am considering a 

different tach sensor or even buying / installing a stand-alone tach as I'm 

getting frustrated in trying to get the IK-2000 engine monitor tach to work 

with the factory recommended sensor.  If anyone has any suggestions on what 

I'm missing in making this work, any input is appreciated.



Here's where I'm at right now:



1.  I cut the Hall effect sensor factory harness as short as I could for 

installing connectors and used a 3-wire shielded cable from there to aft of 

the firewall to connect the Hall effect sensor power, signal, and ground 

wires.  I soldered a short ground wire to the shield at the sensor end of 

the cable and grounded it via ring terminal at the same mag location that I 

grounded the p-lead shield.  No improvement - in fact, probably worse than 

without the shielded cable.



2.  I moved the Hall effect sensor from the right mag to the left mag to see 

if the same noise issue was observed and to see if the problem moved with 

the sensor to the other mag.  The problem DID move to the other mag and was 

identical in performance (or lack thereof).  So the Hall effect sensor gives 

good rpm indication on the IK-2000 as long as the mag it is installed in is 

NOT operating.  As soon as I move the p-lead switch to "On" for the mag the 

sensor is installed on, the tach signal becomes unusable.  At low rpm (below 

about 2000 rpm), the signal usually reads as if no signal is being recieved 

(reads 20 or 30 rpm, same as when IK-2000 energized with engine off).  At 

high power settings, the tach indication bounces between reading correct to 

being 100 to 300 rpm low and the number changes frequently even with 

constant actual engine rpm.  One interesting note is that the tach reading 

is more accurate, i.e. less noise, when the engine is first started and run 

from being cold (ambient temp).  On initial (cold) startup, I start getting 

good tach indication at about 1200 to 1500 rpm, allowing normal runup and 

takeoff, and at cruise power settings everything looks good with the tach. 

After shutdown and subsequent restart following initial flight of the day, I 

don't get a good, or even close, reading until power goes above about 2000 

rpm.  After warmup in flight, tach indication is jumpy and reads low even at 

2200 to 2300 rpm power settings.  At any time, I can get a solid and 

apparently accurate tach reading by securing the mag that has the Hall 

effect sensor installed (I make the "apparently accurate" statement based on 

past operating conditions: throttle position, sound, and airspeed/fuel flow 

performance data, and the fact that the reading goes back to steady, solid 

reading vice jumping around, and the idle readings are where they 

should/have been).



3.  As mentioned below, I tried installing 0.1 uF capacitor between 

signal/gnd with no improvement.  Same for installing 0.1 uF b/w +5V and gnd. 

Whatever noise is being induced is driving the tach signal to point of no 

pulses detected when the mag with sensor installed is operating.  I can't 

physically seperate the sensor line from the mag or the p-lead any more than 

I already have.



Has anybody had success with the Westach Hall effect sensor installed in a 

Slick mag?  Anybody using this combination with an IK-Technologies engine 

monitor?  If so on either, did you encounter any noise issues that had to be 

overcome?



Any advice/help is appreciated.

Thanks,

Chris

RV-6A, N731CK

---

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Jun 17, 2009 11:41 am Post subject: noisy tach signal

At 01:41 AM 6/17/2009, you wrote:

 	  Quote: 	
		  



I have been unable to solve this problem so far and am considering a 

different tach sensor or even buying / installing a stand-alone tach 

as I'm getting frustrated in trying to get the IK-2000 engine 

monitor tach to work with the factory recommended sensor.  If anyone 

has any suggestions on what I'm missing in making this work, any 

input is appreciated.



Here's where I'm at right now:



1.  I cut the Hall effect sensor factory harness as short as I could 

for installing connectors and used a 3-wire shielded cable from 

there to aft of the firewall to connect the Hall effect sensor 

power, signal, and ground wires.  I soldered a short ground wire to 

the shield at the sensor end of the cable and grounded it via ring 

terminal at the same mag location that I grounded the p-lead 

shield.  No improvement - in fact, probably worse than without the 

shielded cable.


	


   <snip>



   Clearly your hall sensor is responding to "ringing"

   in the magnetic circuit associated with the points-

   opening event of the magneto. Have you used a 'scope

   to see what's showing up on the tach signal when

   the magneto is operating? The tach signal is quite

   low in frequency so some form of low-pass filter

   and/or other signal conditioning is indicated.

   Unfortunately, the expected signal from a hard

   switching hall effect sensor is already full of

   high frequency components (cause it's square).

   Rolling this off to get rid of the ringing spikes

   will probably require re-squaring the signal after

   low-pass to get tach input happy.



   In the past, I've use phase locked loops to grab

   the desired suite of low frequency components that

   basically ignores the spikes. What is the sensor

   brand and part number?

        Bob . . .



         ---------------------------------------

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

         ---------------------------------------

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chris_hand(at)comcast.net
Guest

Posted: Wed Jun 17, 2009 1:13 pm Post subject: noisy tach signal

Thanks Bob.  I don't have access to an o-scope so haven't been able to look 

at the signal.  The only filtering I've tried is the simple wiring of a 0.1 

uF cap from signal lead to ground.  My other efforts at solving the problem 

have been trying various wiring routing changes and then changing the sensor 

leads to shielded cable.



The sensor is a Westach Model 720-14R Hall effect sensor that screws into 

the Slick mag vent hole over the rotating magnets.  Westach has been very 

responsive in trying to help solve the issue but no luck so far.  They are 

going to send me a sensor that is driven off the mechanical drive (model 

303DH2T) and I'll see if that works better, but they tell me the setup I 

have has worked for many others and I'm not sure what in my setup could be 

causing the problem.  I haven't heard back from IK-Tech yet.



Chris



 	  Quote: 	
		   

 <nuckolls.bob(at)aeroelectric.com>



   <snip>



   Clearly your hall sensor is responding to "ringing"

   in the magnetic circuit associated with the points-

   opening event of the magneto. Have you used a 'scope

   to see what's showing up on the tach signal when

   the magneto is operating? The tach signal is quite

   low in frequency so some form of low-pass filter

   and/or other signal conditioning is indicated.

   Unfortunately, the expected signal from a hard

   switching hall effect sensor is already full of

   high frequency components (cause it's square).

   Rolling this off to get rid of the ringing spikes

   will probably require re-squaring the signal after

   low-pass to get tach input happy.



   In the past, I've use phase locked loops to grab

   the desired suite of low frequency components that

   basically ignores the spikes. What is the sensor

   brand and part number?

        Bob . . .

- The Matronics AeroElectric-List Email Forum -

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jun 18, 2009 4:00 am Post subject: noisy tach signal

At 04:12 PM 6/17/2009, you wrote:

 	  Quote: 	
		  



Thanks Bob.  I don't have access to an o-scope so haven't been able 

to look at the signal.  The only filtering I've tried is the simple 

wiring of a 0.1 uF cap from signal lead to ground.  My other efforts 

at solving the problem have been trying various wiring routing 

changes and then changing the sensor leads to shielded cable.



The sensor is a Westach Model 720-14R Hall effect sensor that screws 

into the Slick mag vent hole over the rotating magnets.  Westach has 

been very responsive in trying to help solve the issue but no luck 

so far.  They are going to send me a sensor that is driven off the 

mechanical drive (model 303DH2T) and I'll see if that works better, 

but they tell me the setup I have has worked for many others and I'm 

not sure what in my setup could be causing the problem.  I haven't 

heard back from IK-Tech yet.


	


   Hmmm . . . see if the IK-Tech will share a sketch

   of a schematic for the first two stages of tach

   signal conditioning. The manner in which bias levels

   are established for any "squaring" or level sensing

   circuits can have a profound effect on noise sensitivity.

   The schematics (need parts values too) + 'scope trace

   will permit a simple-ideas analysis of the symptoms.

        Bob . . .



         ---------------------------------------

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

         ---------------------------------------

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jun 18, 2009 5:45 pm Post subject: noisy tach signal

At 04:12 PM 6/17/2009, you wrote:

 	  Quote: 	
		  



Thanks Bob.  I don't have access to an o-scope so haven't been able 

to look at the signal.  The only filtering I've tried is the simple 

wiring of a 0.1 uF cap from signal lead to ground.  My other efforts 

at solving the problem have been trying various wiring routing 

changes and then changing the sensor leads to shielded cable.



The sensor is a Westach Model 720-14R Hall effect sensor that screws 

into the Slick mag vent hole over the rotating magnets.  Westach has 

been very responsive in trying to help solve the issue but no luck 

so far.  They are going to send me a sensor that is driven off the 

mechanical drive (model 303DH2T) and I'll see if that works better, 

but they tell me the setup I have has worked for many others and I'm 

not sure what in my setup could be causing the problem.  I haven't 

heard back from IK-Tech yet.


	


   Hmmm . . . see if the IK-Tech will share a sketch

   of a schematic for the first two stages of tach

   signal conditioning. The manner in which bias levels

   are established for any "squaring" or level sensing

   circuits can have a profound effect on noise sensitivity.

   The schematics (need parts values too) + 'scope trace

   will permit a simple-ideas analysis of the symptoms.

        Bob . . .



         ---------------------------------------

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

         ---------------------------------------

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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chris_hand(at)comcast.net
Guest

Posted: Sat Jun 20, 2009 11:36 pm Post subject: noisy tach signal

Thanks Bob, fortunately it appears there was a simple solution that will 

avoid troubleshooting efforts at the circuit level.....it appears the 

720-14R hall effect sender I had installed was defective as I replaced it 

with a new one this evening and after a ground run and short test flight, 

everything seems to be working normally now.



Westach has been very good about helping me with this issue on getting their 

sender to work with the IK unit and they sent me several sender types to 

try, including a new replacement for what I was using.  Excellent customer 

service and tech support from Westach.

I didn't get to the point of using the other sender options they sent as the 

first thing I did was try the straight replacement for what I had.  So my 

lesson learned is that yes, sometimes a brand new sensor/sender can be bad 

right out of the box.  What I don't understand is how a defective hall 

effect sender would cause indications of noise issues when the mag it's 

installed in is running but work normally when that mag is secured.....but 

I've got a working tach now, so I'm happy!



Chris



 	  Quote: 	
		   

 <nuckolls.bob(at)aeroelectric.com>

   Hmmm . . . see if the IK-Tech will share a sketch

   of a schematic for the first two stages of tach

   signal conditioning. The manner in which bias levels

   are established for any "squaring" or level sensing

   circuits can have a profound effect on noise sensitivity.

   The schematics (need parts values too) + 'scope trace

   will permit a simple-ideas analysis of the symptoms.

        Bob . . .

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Jun 21, 2009 10:23 am Post subject: noisy tach signal

At 02:32 AM 6/21/2009, you wrote:

 	  Quote: 	
		  



Thanks Bob, fortunately it appears there was a simple solution that 

will avoid troubleshooting efforts at the circuit level.....it 

appears the 720-14R hall effect sender I had installed was defective 

as I replaced it with a new one this evening and after a ground run 

and short test flight, everything seems to be working normally now.


	


   <snip>

   Great! It would have been interesting to see

   if a 'scope investigation would have revealed

   the problem too . . . but I'm pleased to hear

   that you can move on to more important things!

        Bob . . .



         ---------------------------------------

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

         ---------------------------------------

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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